Response of Auxin, Carbohydrate and Lignin Metabolism to Habitat during the Development of Ginseng Taproot

Abstract

Panax ginseng taproot serves as a crucial storage organ and constitutes a significant component of Chinese herbal medicine. In China, ginseng is cultivated using two primary methods: under-forest planting and farmland planting. These methods create distinct habitats that notably influence the morphology of ginseng taproots. However, the precise regulatory mechanisms governing ginseng taproot expansion remain to be fully elucidated. This study aimed to delineate the patterns of ginseng taproot expansion by examining taproots transplanted into farmland (TCG) and forest environments (TLCG and TQCG). Our findings indicate that light intensity and soil available potassium levels in TCG plots significantly exceed those in TLCG and TQCG plots. Compared with TLCG and TQCG, the taproot diameter of TCG increased by 11.54% and 27.73%, respectively. At the same time, combined with the microstructure of the transverse section of the taproot, it showed that the expansion of the TCG taproot was closely related to cell expansion. During TCG taproot expansion, there was an increase in indole-3-acetic acid (IAA) content, significant starch accumulation, and a decrease in lignin content. By analyzing the expression of key genes, we found that compared with TLCG and TQCG, the expression of genes PgTPS1 and PgALDH1 was upregulated, and the expression of genes PgHCT1, PgPAL3, PgPER3, and PgPER51 were downregulated in TCG taproot. Additionally, the transcription factors PgARF18.1 and PgbHLH42 were identified as responsive to habitat changes, playing pivotal roles in taproot expansion. In conclusion, this study provides foundational insights into the regulatory mechanisms of ginseng taproot expansion, offering significant implications for enhancing the quality and value of ginseng.